Highlight all matches of text dragged with the mouse in the current buffer.
A video capture of msearch in action: msearch.avi.
I use msearch for debugging of automatically generated source code. Usually, there are hundreds of variables and equations in such code. Msearch allows to swiftly change the search string only using the mouse. This makes it easier to trace back how a variable gets its current value through a sequence of equations and assignments.
If you find msearch useful for your own work I would be pleased to read about it. Just leave some note below.